Maybe you've heard of me maybe your haven't. Whited00r creates features for unsupported devices. But one of our developers, Nobita.zzz, has created a complete Siri app install-able via deb package. There is a version for 5.0.1-4.x and 3.1.3. It doesn't require an external proxy or linux. It is in BETA now and crashes should be fixed. We'd love to hear feedback!!

If 3.1.3 version doesn't work try:
delete all from Documents and Library forlder in the app with iFile